[iso1631]

Before 9/11 you hijacked a plane, flew to Cuba, got some money, and all was well.

Before 9/11 you were a passenger/crewmember on a plane, you flew to Cuba, then got released, and all was well.

9/11 changed that. No longer were passengers and crew safe as long as they complied, no longer were planes allowed to fly around and even be refuelled safe in the knowledge that all it would take is some money to free them.

As such over the course of two hours the calculus changed. Hijacking the first 3 planes worked because nobody expected it. The fourth plane was also hijacked, but the goal (crashing into whatever building) wasn't met because the passengers and crew found out the rules had changed.

If you hvae 5 people willing to kill themselves for your cause, there are better ways to make a political statement now than the risk of hijacking a plane - not because of any potential air marshall, but because of the guarantee of the passengers.